operator-keyword

问题 I need to know, first and foremost, if what I'm trying to do is even possible. If it is possible, I then need to know how. It's far easier to demonstrate the problem rather than explain it so here goes: I have an "Enhanced Record" (the purpose - though not important to this question - is to produce a "Smart String" type, to replace the normal String type): TLKString = record Value: String; // Some methods here to operate on and build String values // Allows me to assign String values directly

问题 I am getting a "left side of mutating operator isn't mutable "..<" returns immutable value" error I read the other post regarding mutating values but I can't figure out how those solutions apply. Code (and comments): //populate array of 3 random numbers using correct answer and 2 incorrect choices func insertIntoArray3(_ randomNumber: Int) -> Int { for intJ in 0 ..< 2 += 1{ if arrayIndex != 3 { checkIfExists(randomNumber) if ifExists { let randomNumber = 1 + random() % 10 insertIntoArray3

问题 What would be the most elegant way too fix the following code: #include <vector> #include <map> #include <set> using namespace std; typedef map< int, int > row_t; typedef vector< row_t > board_t; typedef row_t::iterator area_t; bool operator< ( area_t const& a, area_t const& b ) { return( a->first < b->first ); }; int main( int argc, char* argv[] ) { int row_num; area_t it; set< pair< int, area_t > > queue; queue.insert( make_pair( row_num, it ) ); // does not compile }; One way to fix it is

问题 Sorry if this has been asked before. I couldn't find a definitive answer. Can I query on a mongodb index if my query contains the $or operator? My query looks something like this: // find everything in the collection $cursor = $collection->find(array( '$or' => array( array('album_id' => array( '$in' => $this->my_album_ids ), 'type' => array( '$in' => array('like','comment') ) ), array( 'user_id' => (int)session_item('user_id'), 'type' => 'message', 'reply' => 'no' ) ), 'timestamp' => array('

问题 I want to subtract two strings in this code, but it won't let me do it and gives an operator - error. This code basically tries to separate a full input name into two outputs: first and last names. Please Help! Thank you! #include <iostream> #include <cstdlib> #include <string> using namespace std; string employeeName, firstName, lastName; int pos1, difference; int main() { cout << "Enter your full name: " << endl; getline(cin, employeeName); pos1 = employeeName.find(" "); difference = pos1 -

问题 Is it possible/Is there a way to iterate through a sequence of operators as in the following example? a, b = 5, 7 for op in (+, -, *, /): print(a, str(op), b, a op b) One possible use case is the test of the implementation of various operators on some abstract data type where these operators are overloaded. 回答1: You can use the operator module. for op in [('+', operator.add), ('-', operator.sub), ('*', operator.mul), ('/', operator.div)]: print("{} {} {} = {}".format(a, op[0], b, op[1](a, b))

问题 I want to create an operator [] in the case of two dimensional vector. After searching, I have found that it's impossible to pass two arguments. How I can obtain the value of m_matrix[i][j] in the main? relevant code: class MyMatrix { public: // Methods MyMatrix(); ~MyMatrix(); int operator[] (int n); private: // Attributes int m_n; int m_m; std:: vector <std:: vector <int> > m_matrix; }; int MyMatrix::operator[](int n, int m) // in the cpp { if (n>=0 && m>=0 && n<=m_n && m<=m_m) { return m

问题 Considering the following code, I don't understand why "System.out.println( c2 instanceof D);" will result an "illegal compile time error" but not return "false"? Many thanks for your help! interface I { } class A { int x = 1;} class B extends A implements I { int y = 2;} class C extends B { } class D extends B{ } class E implements I { } C c2 = new C();` 回答1: The error from Java 8 is: error: incompatible types: C cannot be converted to D And indeed, C and D are not in the same lineage (other

问题 How can I match all \p{L} but not \p{Alpha} in a regular expression? Is it possible to implement a logical AND in Java's Regexp? If the answer is yes, how can that be achieved? 回答1: Yes, by using a negated character class: [^\P{L}\p{Alpha}] [^\P{L}] matches the same as \p{L} , but the negated character class makes it possible to subtract characters/properties from that set of characters. 回答2: It is possible, but it is Java specific: [\p{L}&&[^\p{Alpha}]] (quote as appropriate in a Java string

问题 This question already has answers here : Reference — What does this symbol mean in PHP? (18 answers) Closed 5 years ago . What does ?: in this line mean? $_COOKIE['user'] ?: getusername($_COOKIE['user']); Thank you. 回答1: It is a shorthand for an if statement. $username = $_COOKIE['user'] ?: getusername($_COOKIE['user']); Is the same as if( $_COOKIE['user'] ) { $username = $_COOKIE['user']; } else { $username = getusername($_COOKIE['user']); } see test suite here: https://3v4l.org/6XMc4 But in